$14.04 @ TCGplayer
As an additional cost to cast this spell, discard X cards.
Firestorm deals X damage to each of X targets.
For example, if you discard four cards, you must target four different creatures and/or players. Firestorm will deal 4 damage to each of them.
The same permanent or player can’t be targeted more than once.
The value of X can’t exceed the number of cards in your hand or the number of available legal targets, whichever is smaller. X can be 0.
